Alectrona
Commercial guideRC62 is the insurer-backed guidance on fire safety for rooftop solar, and a well-engineered commercial system is designed to answer it from the start. Insurers use it as a reference point when they price your cover.
OrientationThis is a plain-English orientation for buyers, not formal fire-safety advice; we confirm the specifics for your site during survey and design.
RC62 is fire-safety guidance for rooftop solar PV published under the RISCAuthority banner, which is the technical body backed by UK property insurers. It exists because a solar array changes the fire profile of a roof: it adds an electrical generator that stays live in daylight, runs DC cabling across the deck, and places equipment over areas the fire service may one day need to reach.
For a finance or facilities director, RC62 matters for a practical reason. Your property insurer is likely to ask how the system addresses it before renewing or extending cover, and the answer is set during design and installation, not afterwards. A system engineered to the relevant standards tends to satisfy the guidance as a by-product of being built properly.
RC62 looks at the fire risks that a rooftop PV array introduces and at the measures that reduce them. The themes are consistent across the guidance: the array stays electrically live whenever there is daylight, so the DC side cannot simply be switched dead the way an AC circuit can; faults in DC cabling, connectors and isolators are a recognised ignition source; and the physical layout of the array affects how safely a roof can be worked on during a fire.
In plain terms it asks three questions. Can the system be isolated quickly and clearly in an emergency? Are the components specified and installed so they do not become the cause of a fire? And is the array laid out so the fire service can reach the roof and work on it. A commercial design answers all three on paper before any panel goes up.
Insurers price the risk they can see. A poorly specified array, with the wrong connectors, undersized cable or sloppy DC terminations, is a known fire claim pattern, and it sits on a high-value asset that the business depends on. So the underwriter wants evidence that the system reduces that risk rather than adding to it.
RC62 gives them a common reference point. When a system is designed to recognised electrical standards, isolates cleanly, uses correctly rated components and is laid out for access, it reads as a managed risk. That can be the difference between cover being offered on normal terms and cover being loaded, restricted, or made conditional on remedial work. Getting this right at design stage is far cheaper than retrofitting it after a survey flags it.
The measures RC62 is concerned with map onto good commercial engineering practice. The same disciplines that make an array perform reliably also make it safer.
For a system over 50 kWp, which sits outside the domestic MCS scheme, the assurance comes from this engineering stack rather than a single certificate: design to BS 7671, commissioning to IEC 62446-1, and the array laid out and documented with fire access in mind. The specifics that matter for your site, including the exact isolation strategy and access layout, are confirmed during survey and design.
The short answer is the DC side. The recognised origins of rooftop PV fire are concentrated on the part of the system RC62 keeps returning to: the high-voltage DC strings between the modules and the inverter, and the connectors, isolators and terminations along them. Understanding the mechanism is what makes the design choices make sense rather than feeling like box-ticking.
The DC arc is the core hazard. A string of modules can sit at several hundred volts in daylight, and that voltage is present continuously, with no zero-crossing. When a connection works loose, corrodes, or is poorly made, current can jump the gap and sustain an arc. Unlike an AC fault, a DC arc does not naturally extinguish at a current zero, so it can keep burning at the fault point and ignite the cable, the connector body, or combustible roof build-up around it. This is the failure RC62 and the wider RISCAuthority fire-safety literature are written around, and it is why the guidance treats DC component quality and termination workmanship as fire controls rather than performance details.
Mismatched and contaminated connectors. A large share of field failures trace to DC connectors of different makes mated together, or to connectors crimped on site without the correct tool. They look connected and test fine on day one, then develop resistance, heat and eventually an arc as they weather. A properly engineered array uses one connector type, mated like-for-like, with factory-style crimps, which is one of the plainest things a loss adjuster or insurer surveyor looks for after an incident. Our guide to BS 7671 and solar sets out the wiring-regulation basis for those terminations, and our note on string versus central inverters explains how the choice of architecture changes how many DC connections exist and how far the high-voltage DC runs across the roof.
Why the array stays live matters here too. Because daylight keeps the DC side energised, a fault cannot be cleared by simply switching the building off, and a fire crew cannot assume a dead roof. That is the link between the ignition mechanism and the access and isolation measures: the same live-in-daylight property that drives clear DC isolation also drives the layout decisions a fire service needs.
RC62 is not only about stopping a fire starting. A large part of its thinking is about what happens if a fire occurs anywhere on or under the building, and whether the array helps or hinders the people who have to deal with it. A commercial roof covered edge to edge in modules is a very different prospect for a fire crew than one designed with their work in mind.
The practical measures are spatial. Set-backs from the roof edge leave a working margin so crews are not operating against live equipment at the perimeter. Walkways and access routes through the array let the roof be reached, ventilated and worked on, and keep the live DC away from the paths people use. Clear zones around roof penetrations, smoke vents and plant keep existing fire-safety features functioning rather than being built over. None of this is retrofittable cheaply, so it is a design-stage decision, settled on the layout before mounting goes down.
This is where fire safety overlaps with the rest of the build. The same set-backs and walkways that serve a fire crew also make the array safe to inspect and maintain over its life, which ties RC62 to the work-at-height duties planned under CDM 2015 and to a workable maintenance regime. A layout that no one can walk is a layout that gets inspected from the ground, which is how faults go unseen. Designing the access in once serves the insurer, the fire service and the engineer who has to keep the system healthy. The exact set-back distances and walkway positions for your roof are a survey-led judgement, confirmed against the building, the array footprint and any local fire-service expectations rather than applied as a fixed rule.
When an underwriter, a surveyor or a loss adjuster looks at a rooftop array, they are looking for a paper trail that shows the fire risks were designed out and are being kept in check. RC62 gives them the reference points; the evidence is what satisfies them. There is no single RC62 certificate to wave, so the assurance is a documented stack, and on a system over 50 kWp, outside the domestic MCS scheme, this documentation is the trust signal.
The core of it is the commissioning and design record. Design to BS 7671 with the DC string voltages and component ratings shown, commissioning and test results to the IEC 62446-1 standard for grid-connected PV inspection and testing, and a clear isolation strategy with DC and AC isolation points labelled and located. Alongside that sits the as-built layout showing set-backs, walkways and access, and the component schedule proving connectors and cable are correctly rated and consistent. Together these answer the three RC62 questions, can it be isolated, are the components safe, can the roof be reached, on paper.
Ongoing evidence matters as much as the handover pack. Insurers increasingly want to see that the system is monitored and inspected over its life, not only that it was built well once. Periodic inspection, including thermographic survey that finds hot connections before they fail, is a recognised way to catch the degrading DC connection that leads to an arc. A live monitoring and inspection regime is what turns a one-off commissioning record into continuing evidence of a managed risk, which is the language an insurer prices on. Our guide to commercial solar insurance covers how cover and these requirements interact, and the maintenance side is set out in the maintenance guide. We assemble this evidence at handover and keep it current through the O&M plan so the system stands up to an insurer's review at every renewal.
Our own insured pilot flies your roof and captures the real geometry and shading, so the design starts from your building instead of a satellite guess.
Booked to suit your operating hours
We model the array in bankable-grade software, size it around your daytime load, and set out generation, savings and payback across three funding routes.
Modelled, not promised
Designed and installed to BS 7671, commissioned to IEC 62446-1, connected under G99 and run under CDM 2015. Alectrona is typically the Principal Contractor.
Outside MCS, assured by the non-MCS stack
A 12-month defects period backed by an Insurance-Backed Guarantee, then ongoing operations and maintenance so the asset keeps earning for its full working life.
Kept performing, year on year
RC62 is insurer guidance rather than a statute, so it is not law in the way the Building Regulations or CDM 2015 are. In practice it carries real weight, because property insurers use it as a reference when they assess a rooftop array, and cover can be made conditional on a system reflecting it.
This is a plain-English orientation, not formal advice. We confirm what applies to your specific building and policy during survey and design.
The AC side can be isolated like any electrical circuit, but the panels themselves generate DC voltage whenever there is daylight on them. That means the DC cabling between the modules and the inverter can stay live even with the building powered down, which is why RC62 puts so much weight on clear DC isolation and labelling.
A well-designed system makes the isolation points obvious and accessible, and signs the array so anyone responding understands the DC side remains live in daylight. Where the fire-safety case is strong, a module-level architecture with rapid shutdown goes further, de-energising the DC at each panel rather than only at the inverter.
It can. Insurers price the risk they can see, and a rooftop array that addresses RC62 reads as a managed risk rather than an added hazard. A system that does not can lead to cover being loaded, restricted, or made conditional on remedial work.
The most reliable way to avoid that is to build it correctly the first time. Designing for clean isolation, correctly rated components and fire access from the outset is far cheaper than retrofitting after an insurer's survey flags a problem.
The fire-safety principles apply to rooftop PV generally, but they carry more weight as systems get larger and sit on higher-value commercial buildings. A commercial array over 50 kWp is outside the domestic MCS scheme, so the assurance for fire safety and everything else comes from the engineering standards and documentation rather than a domestic certificate.
Look for it in the design and commissioning evidence rather than as a single badge. A clear DC and AC isolation strategy, correctly rated and properly mated components, commissioning to IEC 62446-1, and an array layout that keeps firefighter access and roof set-backs in mind are the practical signs the guidance has been built in.
We document these as part of the handover so the system stands up to an insurer's review.
The measures RC62 leans on, clean DC isolation, correctly rated and consistent connectors, commissioning to standard, and a layout with fire-service access, are part of building the array properly rather than a separate add-on, so a well-engineered quote already carries them. Module-level rapid-shutdown architecture, where the fire case calls for it, is the main variable that moves cost. Everything is modelled before we quote, and the first feasibility read is free. See our guide to commercial solar cost.
Not materially, because the fire-safety measures are designed in at the survey and design stage rather than bolted on later. The isolation strategy, component schedule and access layout are settled before mounting begins, so they shape the design programme without extending the on-site install. Retrofitting them after an insurer's survey flags a gap is what costs time, which is the case for getting it right first. Lead times are confirmed once the design and any grid connection are settled, not fixed in advance.
Last updated June 2026
A guide can only take you so far. The figure you get is modelled from your own half-hourly load and a system sized from the on-site drone survey. No obligation, and systems this size sit outside the domestic MCS scheme, so the assurance is the engineering stack.